1. Field of the Invention
The invention relates to a lighting module, more particularly to a lighting module for use in a keypad device.
2. Description of the Related Art
In order that keys on a keypad can be easily identified in a relatively dark environment to facilitate operation of the same, a light source is generally provided behind each key such that light from the light source can pass through a transparent portion of the key to enable the user to discern and operate the keys. However, when applied to a portable electronic or communications device that has a large number of keys, such an arrangement would be conceivably expensive since a large number of light sources is required.
A more economical approach is, as described in U.S. Pat. No. 5,083,240, to provide a light guide plate which is disposed between a light source and keys on a keypad and which extends along the respective keys. The light from the light source is dispersed evenly to each of the keys by total reflection. The number of light sources is therefore considerably decreased, thereby reducing costs.
However, although the use of light guide plates can cut costs, the overall thickness of the device is increased, which goes against the current trend toward miniaturization of portable electronic or communications devices. Therefore, improvements on the structure of the device are required to keep up with the current trend and to enhance the market competitiveness of the device.